In prior art glue guns a stick of solid adhesive, without a casing, is advanced through the gun either by manual pressure, or mechanically. One glue stick is used to push the remains of an earlier stick through the glue gun. Severe limitations exist as to the types of glue which may be used in this type of gun, since most hot melt glue formulas cannot combine the requirement of stick stiffness with properties that maximize the adhesive qualities of the glue. Furthermore, changing the type of glue in the glue gun requires the previous adhesive to be removed from the melt chamber because supplying a different type of adhesive to the melt chamber produces a blended glue which often has properties inferior to those of either of its components.
Cohen U.S. Pat. No. 3,459,335, Siwon U.S. Pat. No. 4,463,877, Steinel U.S. Pat. No. 4,493,972, Dziki U.S. Pat. No. 4,457,457, Cooper U.S. Pat. No. 3,281,576, Juffa U.S. Pat. No. 3,199,740, and Newton U.S. Pat. No. 3,776,426 show prior glue guns each having the disadvantage of using a rod of adhesive, without a casing, in which the formulation of the adhesive is severely limited by the necessity for the rod to be rigid. Also these glue guns include, the requirement of cleaning one glue out of the melt chamber before inserting a glue stick of a different formulation. Further prior art includes MacKinnon U.S. Pat. No. 2,626,085, which describes a grease gun having a plunger for expelling grease from the gun. A caulking gun, such as that shown in DeHart U.S. Pat. No. 3,636,378, dispenses caulk from a cartridge at ambient temperature.